[PETER GUNN]

Hi everyone i hope there is someone who can shed a light on my enquiry, a number of years ago i bought some Parma 16D type motors which have lain dormant for many years, i have decided to strip the lot down with intentions of reusing them when i took them to pieces i found all 5 had modified motor brushes which were cut in a L shape so only half the brush was touching the com obviously this must have been a performance tweak which i have never seen, and i always thought that the motor would run better with the full brush in contact with the com, antbody know of this i will give the set up a try against a standard set to see if there is any difference, hope you scratch builders can help.
Cheers Keith.

 

[merkit the grof]

I think it changes the timing of the motor, although I can't work out in my head if you would get more advance or not
Neat trick in a sealed motor class.

Joel

 

[300SLR]

Hi Keith
Which way round was the L shape? Half of the height touching the comm or half the width touching.

Half of the height touching the comm will change the timing. For this sort of motor, it's much more likely a tuner would want to advance rather than retard the timing.
The left and right side brushes need to be the opposite way up.
Looking from the endbell end, the left brush touching the top half and the right brush touching the bottom half will advance the timing if the motor is rotating the normal way round. (And retard the timing if the motor is rotating in the opposite direction).

Half of the width touching will make no differance to the timing, just reduce the contact area.

Timing is one of the things tuners can use to improve performance. An L shaped brush is a simple way of doing it if you don't want to change anything else, although rotating the comm relative to the stack is the normal way of changing the timing.
Not obvious why you'd want to halve the width.

 

[PETER GUNN]

Thanks Guys the motors in question are all before the advent of sealed cans, 300slr the brushes were as you mentioned so all 5 motors must have had advanced timing as they were of the same configuration looking at what is left of the brushes they look like they have been machined that way as they are very neat and true and comparing them with ordinary one's seem harder in composition.
I have rebuilt one using the best of the brushes, filed a set of brushes and put them in another can and have compared them to standard parma 16d & super parma 16d which i have some of , running them up the one using the best of the brushes shows a distinct higher rev than the one i cobbled together both are better than the standard set up and seem about the same as the super 16d possibly slightly better, from the same period i have quite a lot of motors and have checked a Mura GP 15 which also came from the same source and that has exactly the same set up, also all the springs are much stronger than the standard one's, as i have a large box of spares i will have to rebuild some cars to see how they perform against each other.
Keith.

 

[stoner]

a parma s16d turns in the normal direction ie clockwise and should turn 49000rpm bog standard and the timing is advanced from the factory. with goldust or bigfoot brushes, bearings at both ends and lighter springs you can gain a few more rpm. even more if you put a shorter stack oulaw arm in it and advance the timing a bit more. john